1. Field of the Invention
The present invention relates to a portable electronic device called an IC (integrated circuit) card, which incorporates an IC chip having, among other elements, a nonvolatile memory, a control element such as a CPU (central processing unit) and, a management method for managing the memory. The management method of the present invention allows for the entire memory area to be utilized in an efficient manner.
2. Description of the Related Art
In recent years, IC cards which incorporate IC chips having erasable nonvolatile memory, and control elements such as a CPUs have received a great deal of attention as a new portable data storage medium. An IC card normally has an internal which is accessed by an internal control element for selectively inputting data and outputting data from an external device. Today's IC cards are utilized in the following manner. An IC card issuer assigns areas within the IC Card's memory to be given to service offerers. These areas have become known as "data files". Each service offerer can further divide the assigned area into a plurality of data areas which can be used for numerous functions, including system operation. In the past the card manufacturer had to inform the IC card issuer of the useable memory size in the IC card. There was not way of assuring that the usable memory size stated by the manufacturer was the actual amount available in the IC card because available memory could not be checked.
Similarly, when a card issuer assigns a data file, he cannot check whether or not a data file of a predetermined size is actually assigned in an IC card due to the inability to check available memory.